Straddle vehicle

ABSTRACT

A straddle vehicle includes: a prime mover; a hydraulically actuated main clutch; an oil control valve unit; a power unit case accommodating at least the main clutch; an oil pan mounted beneath the power unit case; a clutch-dedicated pump; a primary filter disposed in an oil passage between the oil pan and the clutch-dedicated pump; and a secondary filter disposed in an oil passage between the clutch-dedicated pump and the oil control valve unit. The primary filter and the secondary filter are mounted on a bottom surface of the power unit case and covered from below by the oil pan.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Japanese PatentApplication No. 2019-123351, filed on Jul. 2, 2019, the entiredisclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to a straddle vehicle such as amotorcycle.

Description of the Related Art

In a power unit of a vehicle such as a motorcycle, an oil is drawn froman oil pan into an oil pump, and the oil discharged from the oil pump issupplied to an oil control valve unit (clutch controller) through aprimary filter and a secondary filter (see Japanese Patent No. 5020765,for example). The primary filter is placed in the oil pan mountedbeneath a crankcase, and the secondary filter is disposed inside thecrankcase.

In the above configuration, when maintenance operations are performed onboth of the primary and secondary filters, the power unit needs to bedisassembled to a sufficient extent. Thus, the efficiency of themaintenance operations is low.

SUMMARY OF THE INVENTION

A straddle vehicle according to one aspect of the present disclosureincludes: a prime mover; a hydraulically actuated main clutch disposedin a power transmission route between the prime mover and a drive wheel;an oil control valve unit that controls flow of a hydraulic oil suppliedto the main clutch; a power unit case accommodating at least the mainclutch; an oil pan mounted beneath the power unit case and retaining anoil; a clutch-dedicated pump that sucks the oil from the oil pan andthat discharges the sucked oil as the hydraulic oil toward the oilcontrol valve unit; a primary filter disposed in an oil passage betweenthe oil pan and the clutch-dedicated pump; and a secondary filterdisposed in an oil passage between the clutch-dedicated pump and the oilcontrol valve unit, wherein the primary filter and the secondary filterare mounted on a bottom surface of the power unit case and covered frombelow by the oil pan.

With the above configuration, both the primary filter and the secondaryfilter are made easily accessible by removing the oil pan. This improvesthe ease of maintenance of the two filters.

In an exemplary configuration, the power unit case and the oil pan maybe shaped to form together an accommodation chamber in which thesecondary filter is accommodated.

With this configuration, the accommodation chamber for the secondaryfilter can easily be formed by mounting the oil pan on the power unitcase.

In an exemplary configuration, the straddle vehicle may further include:a prime mover-dedicated pump that sucks the oil from the oil pan anddischarges the sucked oil toward the prime mover to lubricate the primemover; and another secondary filter disposed in an oil passage betweenthe prime mover-dedicated pump and the prime mover, and suction inletsof the clutch-dedicated pump and the prime mover-dedicated pump maycommunicate with the primary filter.

With this configuration, since the primary filter is used for both theclutch-dedicated pump and the engine-dedicated pump, an increase in thenumber of required components and an increase in size of the spacerequired for arrangement of the components can be prevented.Additionally, since different pumps are used as the clutch-dedicatedpump and the engine-dedicated pump, respectively, the hydraulic oil canbe supplied quickly to the main clutch even at the start-up of the primemover. If a single pump is used for both the clutch and the prime mover,more of the oil will be delivered toward the prime mover (the lowpressure side) than toward the clutch at the start-up of the primemover, and a long time will be required for the main clutch to becomeoperable. With the above configuration, the time required for the mainclutch to become operable can be shortened even at the start-up of theprime mover.

In an exemplary configuration, the clutch-dedicated pump and the primemover-dedicated pump may be coaxially connected to each other.

With this configuration, the straddle vehicle can be made compact.

In an exemplary configuration, the straddle vehicle may further include:a relief valve disposed between the clutch-dedicated pump and the oilcontrol valve unit; and a bypass passage through which the oildischarged from the relief valve is introduced into an oil passagebetween the primary filter and the clutch-dedicated pump without passingthrough the primary filter.

With this configuration, the amount of the oil sucked from the oil panthrough the primary filter can be reduced, and thus the energy loss dueto the passing of the oil through the primary filter can be reduced.

In an exemplary configuration, the power unit case may include anopening communicating with the oil passage between the primary filterand the clutch-dedicated pump, and the power unit case and the oil panmay be shaped to form together a communication chamber as the bypasspassage, the communication chamber communicating with the relief valveand the opening.

With this configuration, the bypass passage can easily be formed bymounting the oil pan on the power unit case.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a motorcycle according to an embodiment.

FIG. 2 is a schematic diagram of a power system of the motorcycle ofFIG. 1.

FIG. 3 is a cross-sectional view showing key components of the powerunit of FIG. 2.

FIG. 4 is a schematic diagram of various shafts and other components ofthe power system of the motorcycle of FIG. 1 as viewed in the vehiclewidth direction.

FIG. 5 is a right rear perspective view of the power unit of themotorcycle of FIG. 1 with covers removed from the power unit.

FIG. 6 is a left rear perspective view of the power unit of FIG. 5.

FIG. 7 is a right side view of the power unit of FIG. 5.

FIG. 8 is a right side view of the power unit of FIG. 7 with the coversmounted thereon.

FIG. 9 is a longitudinal sectional rear view of an extended portion of acrankcase and the vicinity of the extended portion in the power unit ofFIG. 5.

FIG. 10 is a front view of the power unit of FIG. 5 with the coversmounted thereon.

FIG. 11 is a perspective view of the power unit of FIG. 6 with a drivemotor removed therefrom.

FIG. 12 is an enlarged left side view of the drive motor and itsvicinity in the power unit of the FIG. 6.

FIG. 13 is a block diagram illustrating an oil passage of the power unitof FIG. 5.

FIG. 14 is a bottom view of the power unit of FIG. 8.

FIG. 15 is a longitudinal sectional view of a bypass passage in the oilpassage of the power unit of FIG. 14.

FIG. 16 is a longitudinal sectional view of a secondary filter and itsvicinity in the power unit of FIG. 14.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, an embodiment will be described with reference to thedrawings.

FIG. 1 is a side view of a motorcycle 1 according to the embodiment.FIG. 2 is a schematic diagram of a power system of the motorcycle 1 ofFIG. 1. As seen from FIG. 1, the motorcycle 1 is an example of astraddle vehicle on which the rider is seated in a straddling position.The motorcycle 1 is configured as a hybrid vehicle. The motorcycle 1includes a front wheel 2, a rear wheel 3 (drive wheel), a vehicle bodyframe 4, a front suspension 5 connecting the front wheel 2 to a frontportion of the vehicle body frame 4, and a rear suspension 6 connectingthe rear wheel 3 to a rear portion of the vehicle body frame 4. Thefront suspension 5 is coupled to a bracket 7 spaced from the frontsuspension 5 in the upward/downward direction. A steering shaftconnected to the bracket 7 is supported by a head pipe 4 a constitutinga part of the vehicle body frame 4, and the steering shaft is angularlymovable. On the steering shaft is mounted a handle 8 to be held by thehands of the rider. A fuel tank 9 is disposed rearwardly of the handle8, and a seat 10 on which the rider sits is disposed rearwardly of thefuel tank 9. On the vehicle body frame 4 is mounted a power unit 11serving as a drive source for travel, and the power unit 11 is locatedbetween the front and rear wheels 2 and 3.

As shown in FIGS. 1 and 2, the power unit 11 includes an engine E and adrive motor M as prime movers. The engine E is an internal combustionengine, and the drive motor M is an electric motor. A transmission 12 isdisposed rearwardly of the engine E. The transmission 12 includes aninput shaft 12 a, an output shaft 12 b, and a plurality of gear trains12 c having different reduction ratios. The transmission 12 isconfigured to transmit power from the input shaft 12 a to the outputshaft 12 b through the gear trains 12 c and configured to perform speedchange with a selected one of the gear trains 12 c. For example, thetransmission 12 is a dog clutch transmission. The engine E includes acrankshaft Ea, one end of which is connected to a primary gear 17 so asto be capable of power transmission to the primary gear 17. The otherend of the crankshaft Ea is connected to an integrated starter generatorISG so as to be capable of power transmission to the integrated startergenerator ISG.

The primary gear 17 is disposed around the input shaft 12 a and locatedbetween the main clutch 13 and the gear trains 12 c in the axialdirection of the input shaft 12 a. The primary gear 17 is rotatablerelative to the input shaft 12 a. The primary gear 17 transmitsrotational power from the crankshaft Ea to the main clutch 13. Theprimary gear 17 is connected to the input shaft 12 a of the transmission12 via the main clutch 13 so as to be capable of power transmission tothe input shaft 12 a. The main clutch 13 is mounted on one end of theinput shaft 12 a and functions to establish and break the powertransmission route from the crankshaft Ea to the input shaft 12 a. Themain clutch 13 is actuated by hydraulic pressure. The main clutch 13 is,for example, a multi-plate clutch.

In the vicinity of the input shaft 12 a there are disposed aclutch-dedicated pump P1 and an engine-dedicated pump P2 which aremechanically linked to, and driven by, rotation of the input shaft 12 a.The respective driven shafts Pa of the clutch-dedicated pump P1 andengine-dedicated pump P2 are coaxial. The crankshaft Ea of the engine E,the input and output shafts 12 a and 12 b of the transmission 12, themain clutch 13, the clutch-dedicated pump P1, and the engine-dedicatedpump P2 are accommodated in a crankcase 14 (power unit case). Thecrankshaft Ea, input shaft 12 a, output shaft 12 b, and driven shafts Paare parallel to one another and extend in the vehicle width direction ofthe motorcycle 1 (leftward/rightward direction). The vehicle body frame4 supports a swing arm 15 supporting the rear wheel 3 and extending inthe forward/rearward direction, and the swing arm 15 is angularlymovable. The rotational power of the output shaft 12 b of thetransmission 12 is transmitted to the rear wheel 3 through an outputtransmission member 16 (e.g., a chain or belt).

Between the primary gear 17 and the gear trains 12 c is disposed asprocket 18 (rotary member), which is mounted around the input shaft 12a and rotates together with the input shaft 12 a. The drive motor Mincludes a motor housing Ma and a motor drive shaft Mb projecting fromthe motor housing Ma, and a sprocket 19 is mounted on the motor driveshaft Mb to rotate together with the motor drive shaft Mb. Gears orpulleys may be used as the rotary members instead of the sprockets 18and 19. A chain 20 (power transmission member) is connected to both thesprocket 18 mounted on the input shaft 12 a and the sprocket 19 mountedon the motor drive shaft Mb. Thus, the drive power of the drive motor Mis transmitted to the input shaft 12 a through the sprocket 18. That is,the combination of the sprocket 19, chain 20, and sprocket 18 is anexample of a power transmission mechanism 40 that transmits power fromthe motor drive shaft Mb to the input shaft 12 a.

The drive power of the engine E is transmitted to a first one-way clutch21 through the primary gear 17. The drive power of the drive motor M istransmitted to a second one-way clutch 22 through the sprocket 18. Thefirst one-way clutch 21 and second one-way clutch 22 are connected tothe driven shafts Pa of the clutch-dedicated pump P1 andengine-dedicated pump P2 via a power transmission mechanism 23 so as tobe capable of power transmission to the driven shafts Pa. That is, thefirst one-way clutch 21 and second one-way clutch 22 constitute a pumppower transmitter 30 that transmits the drive power of the engine E ordrive motor M to the clutch-dedicated pump P1 and engine-dedicated pumpP2.

An oil discharged from the clutch-dedicated pump P1 is supplied as ahydraulic oil to the main clutch 13 through an oil control valve unit24. The oil control valve unit 24 opens and closes a flow passagethrough which the oil flows from the clutch-dedicated pump P1 to themain clutch 13. An oil discharged from the engine-dedicated pump P2 issupplied as a lubricating oil to the engine E and the transmission 12.An electronic control unit (ECU) 25 controls the engine E. Specifically,the ECU 25 controls a throttle device T, a fuel injection device F, andan ignition device I. The ECU 25 further controls engagement anddisengagement of the main clutch 13 by controlling the opening andclosing of the oil control valve unit 24.

FIG. 3 is a cross-sectional view showing key components of the powerunit 11 of FIG. 2. As shown in FIG. 3, the crankcase 14 includes: a casebody 27 including a main body portion 31 and an extended portion 32(FIG. 5) which are described in detail below; and a first cover 28removably mounted on a lateral side of the case body 27. A second cover29, which is described in detail below, is further mounted on the casebody 27. Inside the case body 27 is formed a main chamber MR (crankchamber). The main chamber MR accommodates the crankshaft Ea and thetransmission 12. The main body portion 31 of the case body 27 includes aside wall portion 31 a provided with a hole H, inside which a bearing 33is mounted. The bearing 33 rotatably supports the input shaft 12 a. Theside wall portion 31 a is located between the primary gear 17 and thegear trains 12 c.

Between the case body 27 and the first cover 28 (and the second cover29) is formed a subsidiary chamber SR. One end of the input shaft 12 aprojects into the subsidiary chamber SR. Although not illustrated inFIG. 3, the driven shafts Pa (see FIG. 4) of the clutch-dedicated pumpP1 and engine-dedicated pump P2 also project into the subsidiary chamberSR. The subsidiary chamber SR accommodates one end of the crankshaft Ea,the one end of the input shaft 12 a, the main clutch 13, the primarygear 17, the pump power transmitter 30, and the driven shafts Pa of theoil pumps P1 and P2.

The main clutch 13 includes an outer case (not illustrated), an innercase (not illustrated), and a multi-plate unit (not illustrated). Whenthe multi-plate unit is brought into a pressed state, the inner casebecomes unable to rotate relative to the outer case, and aclutch-engaged state is established. When the multi-plate unit isbrought into a non-pressed state, the inner case becomes able to rotaterelative to the outer case, and a clutch-disengaged state isestablished. The outer case of the main clutch 13 is coupled to theprimary gear 17 to rotate together with the primary gear 17. The innercase of the main clutch 13 is coupled to the input shaft 12 a to rotatetogether with the input shaft 12 a. The inner diameter of the primarygear 17 is larger than the outer diameter of the input shaft 12 a, andthe inner peripheral surface of the primary gear 17 is spaced radiallyoutward from the outer peripheral surface of the input shaft 12 a.

The input shaft 12 a is hollow. Inside the input shaft 12 a are formed afirst flow passage S1 and a second flow passage S2 which are dividedfrom each other. The first flow passage S1 opens to the outside at oneend of the input shaft 12 a, while the second flow passage S2 opens tothe outside at the other end of the input shaft 12 a. The input shaft 12a includes a first opening 12 d through which the first flow passage S1communicates with an inlet port 13 a of the main clutch 13. The inputshaft 12 a includes a second opening 12 e through which a lubricatingoil is supplied from the second flow passage S2 to the main clutch 13.The first cover 28 includes a fitting portion 28 a tightly fitted on theone end of the input shaft 12 a.

In the first cover 28 is formed a hydraulic oil passage 28 bcommunicating with the oil control valve unit 24 (see FIG. 2). Thehydraulic oil passage 28 b communicates with the first flow passage S1at the inside of the fitting portion 28 a. When a hydraulic pressurelarger than a predetermined pressure is applied from the hydraulic oilpassage 28 b of the first cover 28 to the main clutch 13 through thefirst flow passage S1 of the input shaft 12 a, the main clutch 13 isbrought into an engaged state. When the hydraulic pressure transmittedfrom the hydraulic oil passage 28 b of the first cover 28 to the mainclutch 13 through the first flow passage S1 of the input shaft 12 afalls below the predetermined pressure, the main clutch 13 is broughtinto a disengaged state.

The pump power transmitter 30 is configured to receive power transmittedfrom the crankshaft Ea of the engine E through the primary gear 17 andpower transmitted from the drive motor M through the input shaft 12 aand sprocket 18 and configured to appropriately transmit the power ofthe crankshaft Ea and the power of the drive motor M to the drivenshafts Pa of the clutch-dedicated pump P1 and engine-dedicated pump P2.The pump power transmitter 30 includes the first one-way clutch 21, thesecond one-way clutch 22, and a common gear 34 (tubular member). Asprocket or pulley may be used as the tubular member instead of thecommon gear 34.

The sprocket 18, to which the drive power of the drive motor M istransmitted, is located closer to the gear trains 12 c than is theprimary gear 17. Specifically, the sprocket 18 is disposed between theprimary gear 17 and the bearing 33 mounted in the side wall portion 31 aof the case body 27. Thus, the chain 20 (see FIGS. 2 and 5) connected tothe sprocket 18 is prevented from being located outwardly of the mainclutch 13 in the vehicle width direction, and an increase in vehiclewidth can be prevented.

The primary gear 17 includes a tubular portion 17 a projecting towardthe sprocket 18 from an inner peripheral portion of the primary gear 17.The first one-way clutch 21 is fitted around the tubular portion 17 a ofthe primary gear 17. The sprocket 18 includes: a tubular portion 18 awhich is an inner peripheral portion fitted around the input shaft 12 aso that the sprocket 18 rotates together with the input shaft 12 a; anannular plate portion 18 b projecting radially outward from the tubularportion 18 a; and a power receiving portion 18 c which is a teethportion disposed on the outer periphery of the annular plate portion 18b and having the chain 20 connected thereto. The tubular portion 18 aprojects toward the primary gear 17 from the annular plate portion 18 b.The portions of the sprocket 18 need not be integrally formed; forexample, the tubular portion 18 a and the annular plate portion 18 b maybe separately formed and secured to each other.

The second one-way clutch 22 is fitted around the tubular portion 18 aof the sprocket 18. The second one-way clutch 22 is located closer tothe sprocket 18 than is the first one-way clutch 21. The first one-wayclutch 21 and second one-way clutch 22 are disposed around the inputshaft 12 a and adjacent to each other in the direction of the axis X ofthe input shaft 12 a. The rotational power of the primary gear 17 istransmitted to the first one-way clutch 21, and the rotational power ofthe input shaft 12 a is transmitted to the second one-way clutch 22.

The first one-way clutch 21 and second one-way clutch 22 are fittedinside the common gear 34. The first one-way clutch 21 transmits powerin the direction from the primary gear 17 toward the common gear 34, butdoes not transmit power in the direction from the common gear 34 towardthe primary gear 17. The second one-way clutch 22 transmits power in thedirection from the sprocket 18 toward the common gear 34, but does nottransmit power in the direction from the common gear 34 toward thesprocket 18. Since the two adjacent one-way clutches 21 and 22 arefitted inside the common gear 34, an increase in the number of requiredcomponents can be prevented, and a reduction of the size of the pumppower transmitter 30 in the direction of the axis X can be achieved. Thecommon gear 34 is connected to the driven shafts Pa of theclutch-dedicated pump P1 and engine-dedicated pump P2 so as to becapable of power transmission to the driven shafts Pa, and thisconnection is made via a gear serving as the power transmissionmechanism 23.

The primary gear 17 includes a recessed portion 17 b recessed toward themain clutch 13 in the direction of the axis X. The recessed portion 17 bis located radially outward of, and adjacent to, the tubular portion 17a. A part of the first one-way clutch 21 and a part of the common gear34 are placed in the recessed portion 17 b. In other words, the firstone-way clutch 21 and the common gear 34, as viewed in the radialdirection of the primary gear 17, overlap the primary gear 17. Thus, thepower system can be made compact in the vehicle width direction.

In the sprocket 18, the power receiving portion 18 c is offset withrespect to the annular plate portion 18 b in a direction away from theside wall portion 31 a; namely, the power receiving portion 18 c isoffset outwardly in the vehicle width direction. As such, even when thesprocket 18 is configured to have a large diameter, the side wallportion 31 a of the case body 27 is unlikely to interfere with thesprocket 18. Thus, the flexibility in shape design of the case body 27can be increased. The sprocket 18 includes a recessed portion 18 dlocated between the tubular portion 18 a and the power receiving portion18 c and recessed in a direction away from the main clutch 13 along theaxis X (a direction toward the main chamber MR). The recessed portion 18d is disposed radially outward of, and adjacent to, the tubular portion18 a. A part of the second one-way clutch 22 and a part of the commongear 34 are placed in the recessed portion 18 d. In other words, thesecond one-way clutch 22 and the common gear 34, as viewed in the radialdirection of the sprocket 18, overlap the sprocket 18. Thus, the powersystem can be made compact in the vehicle width direction.

The sprocket 18 is larger in diameter than the gears of the gear trains12 c. The sprocket 18 is larger in diameter than the common gear 34. Thesprocket 18 is disposed in the subsidiary chamber SR in which the mainclutch 13 having a relatively large diameter is disposed, rather than inthe main chamber MR in which the transmission 12 is disposed. Thus, evenwhen the sprocket 18 has a large diameter, a size increase of thecrankcase 14 can be prevented. Additionally, since the sprocket 18 isdisposed in the subsidiary chamber SR, the sprocket 18 can be configuredto have a large diameter such that the speed of rotation produced by thedrive power transmitted from the drive motor M to the input shaft 12 ais reduced at a sufficient reduction ratio. This can prevent a sizeincrease of the drive motor M. Hence, in the hybrid motorcycle 1 inwhich the drive power of the drive motor M is transmitted to the inputshaft 12 a of the transmission 12, a size increase of the power systemcan be prevented.

FIG. 5 is a right rear perspective view of the power unit 11 of themotorcycle 1 of FIG. 1 with the covers removed from the power unit 11.FIG. 6 is a left rear perspective view of the power unit 11 of FIG. 5.FIG. 7 is a right side view of the power unit 11 of FIG. 5. FIG. 8 is aright side view of the power unit of FIG. 7 with the covers mountedthereon. FIG. 9 is a longitudinal sectional rear view of the extendedportion 32 of the crankcase 14 and the vicinity of the extended portion32 in the power unit 11 of FIG. 5. FIG. 10 is a front view of the powerunit 11 of FIG. 5 with the covers mounted thereon. As shown in FIGS. 5to 8, the power unit 11 includes the engine E and the drive motor M. Theengine E includes a cylinder Eb extending upwardly from a front portionof the crankcase 14. The crankcase 14 includes the main body portion 31projecting rearwardly from a lower portion of the cylinder Eb. The drivemotor M is disposed rearwardly of the cylinder Eb and mounted on the topsurface of the main body portion 31. That is, the drive motor M isaligned with the main body portion 31 in the upward/downward direction.

The drive motor M includes the motor housing Ma which is approximatelyin the shape of a circular tube, and the motor drive shaft Mb projectsto one side (toward the subsidiary chamber SR) in the vehicle widthdirection. The crankcase 14 further includes the extended portion 32projecting upwardly from the main body portion 31 so as to be locatedlateral to the motor housing Ma. Thus, the extended portion 32 as viewedfrom the one side in the vehicle width direction overlaps the drivemotor M. The upper end of the extended portion 32 is at a lower levelthan the upper end of the drive motor M. One end of the motor driveshaft Mb is inserted into the extended portion 32.

The case body 27 includes a frame-shaped wall portion 31 b projectingoutwardly (toward the main clutch 13) in the vehicle width directionfrom the side wall portion 31 a of the main body portion 31 defining themain chamber MR. The frame-shaped wall portion 31 b has an opening 31 cfacing outwardly in the vehicle width direction. The first cover 28 isremovably secured to the outer end face of the frame-shaped wall portion31 b in the vehicle width direction so as to close the opening 31 c. Theextended portion 32 has an opening 32 d facing outwardly in the vehiclewidth direction, and the second cover 29 is removably secured to theframe-shaped outer end face of the extended portion 32 in the vehiclewidth direction so as to close the opening 32 d. The case body 27includes a bridge portion 37 dividing the opening 31 c from the opening32 d and connecting the end face of the frame-shaped wall portion 31 bto the end face of a frame-shaped wall portion 32 b.

A space surrounded by the side wall portion 31 a, frame-shaped wallportion 31 b, and first cover 28 and a space surrounded by the extendedportion 32 and second cover 29 constitute the subsidiary chamber SR. Thesubsidiary chamber SR includes a first region R1 defined by the mainbody portion 31 and a second region R2 defined by the extended portion32. The second region R2 communicates with the first region R1 in theupward/downward direction. The first cover 28 closes the first region R1from outside in the vehicle width direction. The second cover 29 closesthe second region R2 from outside in the vehicle width direction. Sincethe cover closing the subsidiary chamber SR is divided into the firstcover 28 and second cover 29 which are separate from each other, theindividual covers 28 and 29 can be prevented from having a large areaeven when the size of the subsidiary chamber SR is increased by thepresence of the extended portion 32. Thus, noise due to vibration of thecovers can be reduced.

As shown in FIG. 9, the motor housing Ma of the drive motor M includes aprojecting tubular portion Mc into which the motor drive shaft Mb isinserted. The extended portion 32 of the crankcase 14 includes a sidewall portion 32 a facing the motor housing Ma and a frame-shaped wallportion 32 b projecting outwardly in the vehicle width direction fromthe periphery of the side wall portion 32 a and continuous with the mainbody portion 31. The side wall portion 32 a of the extended portion 32is provided with an insertion hole 32 c. The projecting tubular portionMc of the motor housing Ma is inserted into the insertion hole 32 c. Anannular sealing member 35 is interposed between the inner peripheralsurface of the insertion hole 32 c and the outer peripheral surface ofthe projecting tubular portion Mc. The motor drive shaft Mb projectsoutwardly in the vehicle width direction from the projecting tubularportion Mc. That is, the motor drive shaft Mb extends through theinsertion hole 32 c and projecting tubular portion Mc and leads to thesecond region R2 defined inside the extended portion 32. Thus, the motorhousing Ma and the extended portion 32 are easily connected by fitting.An annular sealing member 36 is disposed in a gap between the motordrive shaft Mb and the projecting tubular portion Mc.

The sprocket 19 is located in the second region R2 of the subsidiarychamber SR and mounted on the outer end of the motor drive shaft Mb. Thechain 20 wound around both the sprocket 19 mounted on the motor driveshaft Mb and the sprocket 18 mounted on the input shaft 12 a isaccommodated in the subsidiary chamber SR and lies partly in the secondregion R2 and partly in the first region R1.

Since the sprockets 18 and 19 are disposed in the subsidiary chamber SRwhich can be opened by removing the first and second covers 28 and 29,the work of mounting and dismounting the chain 20 on and from thesprockets 18 and 19 can easily be performed. Additionally, since thepower transmission mechanism 40 which transmits drive power from themotor drive shaft Mb to the input shaft 12 a is entirely accommodated inthe crankcase 14, a size increase of the power system can be prevented,and lubrication of the power transmission mechanism 40 can easily beaccomplished along with lubrication of the main clutch 13.

As shown in FIG. 7, the chain 20 is held between a front chain guide 38and a rear chain guide 39 in the forward/rearward direction and guidedby these guides. A chain tensioner 41 is mounted on the rear surface ofthe case body 27 of the crankcase 14, and the chain tensioner 41 biasesthe rear chain guide 39 toward the chain 20. This prevents loosening ofthe chain 20. On the rear surface of the cylinder Eb is mounted a chaintensioner 42 that prevents loosening of a chain (not illustrated)mechanically connecting a valve actuator (not illustrated) disposedabove the cylinder Eb to the crankshaft Ea.

As shown in FIGS. 6 and 9, the end face of the frame-shaped wall portion32 b of the extended portion 32 is inclined to extend inwardly in thevehicle width direction from bottom to top. Thus, in a rear view, thechain tensioner 42 protrudes outwardly of the extended portion 32 in thevehicle width direction. As such, even when the extended portion 32 andthe chain tensioner 42 are at least partly at the same location in theupward/downward direction, the chain tensioner 42 is easily accessiblefrom the rear.

As shown in FIG. 8, the crankcase 14 includes an engine lubricating oilpassage 43 through which flows a lubricating oil for lubrication of theengine E and a motor power system lubricating oil passage 44 branchingfrom the engine lubricating oil passage 43. The motor power systemlubricating oil passage 44 is formed in the extended portion 32. Inparticular, the motor power system lubricating oil passage 44 is formedpartly in the case body 27 and partly in the second cover 29. The motorpower system lubricating oil passage 44 includes an upstream passage 44a formed in the frame-shaped wall portion 32 b of the extended portion32 and a downstream passage 44 b formed in the second cover 29 andcommunicating with the upstream passage 44 a. The upstream passage 44 aand downstream passage 44 b communicate at a contact plane between therespective end faces of the frame-shaped wall portion 32 b and secondcover 29.

The second cover 29 includes a discharge outlet 44 c through which thelubricating oil flowing in the downstream passage 44 b is dischargedinto the second region R2. Through the discharge outlet 44 c, the oil isejected toward meshing portions of the sprocket 19 and chain 20. In thisconfiguration, part of the lubricating oil flowing through the enginelubricating oil passage 43 for lubrication of the engine can be used forlubrication of the sprocket 19 and chain 20 in the second region R2.Thus, the lubrication structure can be simplified. Additionally, sincethe lubricating oil is discharged from the second cover 29 rather thanfrom the case body 27, the flexibility in setting the location ofdischarge of the lubricating oil is increased. Beneath the crankcase 14is mounted an oil pan 45 retaining the oil falling from the main chamberMR and the subsidiary chamber SR.

As shown in FIGS. 5, 7, 8, and 10, the oil control valve unit 24 whichcontrols flow of the hydraulic oil supplied to the main clutch 13 issecured to the case body 27 of the crankcase 14. Since the oil controlvalve unit 24 is secured to the case body 27 rather than to the firstcover 28, the oil control valve unit 24 does not obstruct the work ofmounting and dismounting the first cover 28, and the efficiency ofmaintenance operations is improved. Additionally, since the oil controlvalve unit 24 is secured to the case body 27 rather than to the vehiclebody frame 4, the hydraulic oil passage from the oil control valve unit24 to the main clutch 13 can be shortened. In particular, the oilcontrol valve unit 24 is secured to a lower front portion of the casebody 27. As such, interference of the oil control valve unit 24 withother components can be avoided, and the oil control valve unit 24 canbe disposed in a compact manner. The oil control valve unit 24 has anelongated shape and extends longitudinally in the forward/rearwarddirection. Thus, the power system can be made compact in the vehiclewidth direction.

As seen from FIG. 7, when the power unit is viewed in the vehicle widthdirection, the upper end of the oil control valve unit 24 is locatedabove the lower end of the case body 27, and the rear end of the oilcontrol valve unit 24 is located rearwardly of the front end of the casebody 27. This provides a reduction in the length over which the oilcontrol valve unit 24 as viewed in the vehicle width direction projectsfrom the case body 27. The frame-shaped wall portion 31 b of the mainbody portion 31 of the case body 27 includes a lower edge portion 31 ba,a front edge portion 31 bb, and an inclined portion 31 bc extendingobliquely forward and upward from the lower edge portion 31 ba to thefront edge portion 31 bb. The side wall portion 31 a of the main bodyportion 31 has a mounting surface 31 g (see FIG. 10) located forwardlyof and below the inclined portion 31 c when viewed in the vehicle widthdirection.

As shown in FIG. 10, the mounting surface 31 g is located inwardly ofthe outer end face of the frame-shaped wall portion 31 b in the vehiclewidth direction. The oil control valve unit 24 is secured to themounting surface 31 g. The rear end portion of the oil control valveunit 24 is at the same location in the vehicle width direction as thesubsidiary chamber SR. The outer end of the oil control valve unit 24 inthe vehicle width direction is located inwardly of the outer end of thecrankcase 14 in the vehicle width direction. Thus, the length over whichthe oil control valve unit 24 projects from the crankcase 14 is so smallthat the power unit 11 can be made compact and that when the vehicleoverturns, the contact of the oil control valve unit 24 with the groundcan be reduced. The oil control valve unit 24 is secured to the mountingsurface 31 g by fastening fastener elements B onto the mounting surface31 g from outside to inside in the vehicle width direction. As such,mounting and dismounting of the oil control valve unit 24 can easily beperformed by access from outside in the vehicle width direction.

As shown in FIGS. 3, 7, and 8, the main clutch 13 includes the inletport 13 a into which the hydraulic oil is supplied. The first cover 28includes the hydraulic oil passage 28 b into which flows the oil comingout of the oil control valve unit 24. The oil coming out of the oilcontrol valve unit 24 flows in the hydraulic oil passage 28 b of thefirst cover 28 and passes through the first flow passage S1 of the inputshaft 12 a to enter the inlet port 13 a of the main clutch 13. Thus, thehydraulic oil passage from the oil control valve unit 24 to the mainclutch 13 can be formed with a small number of components. The flowoutlet of the oil control valve unit 24 and the flow inlet of thehydraulic oil passage 28 b may be directly connected to each other, maybe connected via a flow passage formed in the main body portion 31, ormay be connected via a tube.

As shown in FIG. 10, the second cover 29 is located inwardly of thefirst cover 28 in the vehicle width direction. Thus, the size of thecrankcase 14 is effectively reduced to allow another component (such asa portion 4 b of the vehicle body frame 4) to be disposed in a spaceoutward of the second cover 29 in the vehicle width direction. Anincrease in vehicle width can therefore be prevented. The bottom surfaceof the main body portion 31 of the case body 27, as viewed from thefront, is provided with a recessed portion 31 e recessed upwardly. Anexhaust pipe 46 connected to an exhaust port of the cylinder Eb passesthrough the recessed portion 31 e from front to rear.

FIG. 11 is a perspective view of the power unit 11 of FIG. 6 with thedrive motor M removed therefrom. FIG. 12 is an enlarged left side viewof the drive motor M and its vicinity in the power unit 11 of FIG. 6. Asshown in FIGS. 11 and 12, the main body portion 31 of the crankcase 14includes an upper wall portion 31 f, and the upper wall portion 31 fincludes front mount portions 47, rear mount portions 48, and a case topsurface 49. Each of the front and rear mount portions 47 and 48 is, forexample, a base provided with a bolt hole, and projects upwardly fromthe upper wall portion 31 f of the main body portion 31. The front ofthe motor housing Ma is secured to the front mount portions 47 fromabove by fastener elements B. The rear of the motor housing Ma issecured to the rear mount portions 48 from above by fastener elements B.That is, the electric motor M is supported by the front and rear mountportions 47 and 48 of the crankcase 14.

The case top surface 49 is formed between the front mount portions 47and the rear mount portions 48 and has a circular arc shape conformingto the outer peripheral surface of the motor housing Ma. The motorhousing Ma is located in proximity to the case top surface 49 andslightly spaced from the case top surface 49. The drive motor M isdisposed in such a manner that a lower portion of the motor housing Mais held between the front mount portions 47 and the rear mount portions48. As such, the drive motor M can be stably supported by the crankcase14.

The case body 27 of the crankcase 14 includes a breather portion 50projecting upwardly from the main body portion 31 accommodating thecrankshaft Ea and the transmission 12. The breather portion 50 defines abreather chamber BR into which blowby gas is introduced from the mainchamber MR. For example, the breather chamber BR has a labyrinthstructure and separates oil mist coming from the main chamber MR intoair and oil. The breather portion 50 is formed between the front of thecase top surface 49 and the main body portion 31 by making use of thecircular arc shape of the case top surface 49 which is downwardlyrecessed.

In particular, the breather portion 50 has a facing surface 50 a facingthe outer peripheral surface of the motor housing Ma, and the facingsurface 50 a as viewed in the vehicle width direction has a circular arcshape. In other words, the facing surface 50 a of the breather portion50 constitutes a part of the case top surface 49. The drive motor M isdisposed rearwardly of the cylinder Eb of the engine E and separatedfrom the cylinder Eb by a gap G. The breather portion 50 is disposed inthe gap G and located rearwardly of the cylinder Eb and forwardly of thedrive motor M. The front mount portions 47 are spaced rearwardly fromthe cylinder Eb of the engine E.

With this configuration, the breather portion 50 can be efficientlyarranged even though the drive motor M is disposed rearwardly of thecylinder Eb of the engine E and mounted on the top surface of thecrankcase 14. As such, the engine E, the crankcase 14, and the drivemotor M can be closely arranged, and a size reduction of the motorcycle1 can be achieved. Additionally, heat transfer from the cylinder Eb tothe drive motor M can be reduced. Further, since the cylinder Eb and thefront mount portions 47 are independent of each other, a process such asmachining can easily be performed.

The top portion of the breather portion 50 is provided with a connectionport 50 b to which a breather tube 51 is connected. The connection port50 b is at the same location in the forward/rearward direction as thefront mount portions 47. Specifically, the front mount portions 47 (twofront mount portions 47 in FIG. 11) are aligned in the vehicle widthdirection. The connection port 50 b is disposed between the pair offront mount portions 47 spaced from each other in the vehicle widthdirection. To the connection port 50 b is connected one end of thebreather tube 51. The other end of the breather tube 51 is connected toan air cleaner box 52 disposed above the drive motor. The air cleanerbox 52 forms an intake passage for introduction of intake air into thecylinder Eb and purifies the intake air. The blowby gas from which theoil has been separated in the breather chamber BR is delivered into theair cleaner box 52 through the breather tube 51.

The breather tube 51 extends upwardly from the breather portion 50 andpasses through the gap G toward the air cleaner box 52. Thus, thebreather tube 51 can be efficiently arranged by making use of the gap Gbetween the cylinder Eb of the engine E and the drive motor M, and thespace efficiency is therefore increased. Additionally, since theconnection port 50 b is at the same location in the forward/rearwarddirection as the front mount portions 47 spaced rearwardly from thecylinder Eb, the breather tube 51 can easily be attached to theconnection port 50 b while the breather tube 51 is maximally spaced fromthe cylinder Eb.

FIG. 13 is a block diagram illustrating the oil passage of the powerunit 11 of FIG. 5. As shown in FIG. 13, the oil retained in the oil pan45 is sucked to a strainer 60 under the action of sucking pressuresgenerated by the clutch-dedicated pump P1 and engine-dedicated pump P2,and the sucked oil is filtered through a primary filter 61 attached tothe strainer 60 and drawn into the clutch-dedicated pump P1 andengine-dedicated pump P2.

The oil discharged from the clutch-dedicated pump P1 passes through arelief valve 62, then is filtered through a secondary filter 63, andreaches the oil control valve unit 24. Once the pressure of the oilflowing from the clutch-dedicated pump P1 to the oil control valve unit24 exceeds a predetermined relief pressure, the relief valve 62 operatesto discharge the oil into a bypass passage 64. The bypass passage 64communicates with a flow passage between the primary filter 61 and theclutch-dedicated pump P1 (and the engine-dedicated pump P2).

When the flow outlet of the oil control valve unit 24 is closed, therelief valve 62 is brought into a relief state once the hydraulicpressure applied to the relief valve 62 exceeds the relief pressure.While the relief valve 62 is in the relief state, the oil delivered fromthe clutch-dedicated pump P1 is discharged from the relief valve 62 intothe bypass passage 64 and returned to a point upstream of theclutch-dedicated pump P1 (and the engine-dedicated pump P2). In thismanner, the amount of the oil sucked from the oil pan 45 through theprimary filter 61 can be reduced, and thus the energy loss due to thepassing of the oil through the primary filter 61 can be reduced.

Once the flow outlet of the oil control valve unit 24 is opened, therelief valve 62 is brought into a normal state, where the oil deliveredfrom the clutch-dedicated pump P1 passes through the relief valve 62,then is filtered through the secondary filter 63, and supplied as thehydraulic oil to the main clutch 13 (in particular its inlet port 13 a)through the oil control valve unit 24. The oil discharged from theengine-dedicated pump P2 is filtered through a secondary filter 65 andsupplied to a main gallery 67 in the engine lubricating oil passage 43of the engine E.

Since the primary filter 61 is used for both the clutch-dedicated pumpP1 and the engine-dedicated pump P2, an increase in the number ofrequired components and an increase in size of the space required forarrangement of the components can be prevented. Additionally, since theclutch-dedicated pump P1 and the engine-dedicated pump P2 areindependent of each other and are not used for the same purpose, thehydraulic oil can, even at the start-up of the engine E, be suppliedquickly to the main clutch 13 before the main gallery 67 is filled withthe oil. As such, the time required for the main clutch 13 to becomeoperable can be shortened even at the start-up of the engine E.

FIG. 14 is a bottom view of the power unit 11 of FIG. 8. As shown inFIG. 14, a frame-shaped mounting seat 79 on which the oil pan 45 ismounted is disposed on the bottom surface of the crankcase 14 (inparticular its case body 27). The frame-shaped mounting seat 79surrounds a region of the bottom surface of the crankcase 14, and thestrainer 60 with the primary filter 61 attached thereto and thesecondary filter 63 are disposed in the region surrounded by themounting seat 79 and are covered from below by the oil pan 45. With theoil pan 45 removed from the mounting seat, the strainer 60 and thesecondary filter 63 as viewed from below are exposed to the outside.Thus, both the primary filter 61 and the secondary filter 63 are madeeasily accessible by removing the oil pan 45. This improves the ease ofmaintenance of the two filters 61 and 63.

The strainer 60 is connected to a flow inlet 70 opening at the bottomsurface of the crankcase 14. The oil sucked to the strainer 60 andfiltered through the primary filter 61 flows into the flow inlet 70. Thecrankcase 14 includes a first flow passage 71 in which the oil enteringthe crankcase 14 through the flow inlet 70 flows toward the suctioninlet 26 a of the clutch-dedicated pump P1 (and the suction inlet 26 bof the engine-dedicated pump P2). The crankcase 14 includes a secondflow passage 72 in which the oil discharged from the clutch-dedicatedpump P1 flows toward the secondary filter 63. The second flow passage 72includes a portion located close to the first flow passage 71 andextending parallel to the first flow passage 71. The crankcase 14includes a third flow passage 73 in which the oil filtered through thesecondary filter 63 flows toward the flow inlet of the oil control valveunit 24.

FIG. 15 is a longitudinal sectional view of the bypass passage 64 in theoil passage of the power unit 11 of FIG. 14. As shown in FIGS. 14 and15, the bottom surface of the crankcase 14 is provided with an opening71 a communicating with the first flow passage 71 between the primaryfilter 61 and the clutch-dedicated pump P1 and facing toward the oil pan45. The bottom surface of the crankcase 14 is further provided with anopening 72 a communicating with the second flow passage 72 between theclutch-dedicated pump P1 and the secondary filter 63 and facing towardthe oil pan 45, and the relief valve 62 is connected to the opening 72a. The opening 72 a is formed in that portion of the second flow passage72 which is located close to the first flow passage 71 and extendsparallel to the first flow passage 71.

The bottom surface of the crankcase 14 is provided with a surroundingwall portion 74 which, as viewed from below, projects downwardly tosurround both the opening 71 a and the relief valve 62. The lower edgeof the surrounding wall portion 74 faces the oil pan 45. The bottomsurface of the crankcase 14, the inner peripheral surface of thesurrounding wall portion 74 of the crankcase 14, and the top surface ofthe oil pan 45 define a communication chamber 75. While the relief valve62 is in the relief state, the oil discharged from the relief valve 62is returned to the first flow passage 71 through the communicationchamber 75 and the opening 71 a. That is, the communication chamber 75serves the function of the bypass passage 64.

In this configuration, the bypass passage 64 can easily be formed bymounting the oil pan 45 on the crankcase 14. A sealing member may bedisposed between the lower end face of the surrounding wall portion 74and the oil pan 45. The surrounding wall portion 74 may be configured toproject from the oil pan 45 rather than from the crankcase 14 or may beconfigured to have opposing portions which project from the crankcase 14and the oil pan 45, respectively.

FIG. 16 is a longitudinal sectional view of the secondary filter 63 andits vicinity in the power unit 11 of FIG. 14. As shown in FIGS. 14 and16, the bottom surface of the crankcase 14 (in particular its case body27) is provided with a recessed portion 76 recessed upwardly. The secondflow passage 72 opens into the recessed portion 76, and the third flowpassage 73 also opens into the recessed portion 76. Thus, the secondflow passage 72 communicates with the third flow passage 73 through therecessed portion 76.

The top surface of the oil pan 45 is provided with a recessed portion 77recessed downwardly. With the oil pan 45 mounted on the crankcase 14,the recessed portion 76 and the recessed portion 77 are combined to forman accommodation chamber 78. The secondary filter 63 is accommodated inthe accommodation chamber 78. The accommodation chamber 78 for thesecondary filter 63 can easily be formed merely by mounting the oil pan45 on the crankcase 14. The oil pan 45 need not necessarily be providedwith the recessed portion 77 as long as the crankcase 14 and the oil pan45 are shaped to form together the accommodation chamber 78.

The present invention is not limited to the embodiment described above,and modifications, additions, or omissions can be made to theconfiguration of the above embodiment. For example, while in the aboveembodiment the clutch-dedicated pump P1 and the engine-dedicated pump P2are mechanical pumps driven by power of the engine E, at least one ofthe clutch-dedicated pump P1 and the engine-dedicated pump P2 may be anelectrically-driven pump. While in the above embodiment the crankcase ispresented as an example of the power unit case, a case accommodating thedrive motor may serve as the power unit case when the vehicle does notinclude the engine E but only the drive motor as a prime mover. While inthe above embodiment the two covers, namely the first cover 28 andsecond cover 29, are provided as the covers closing the subsidiarychamber SR, a single large cover may be used to close the entiresubsidiary chamber SR. The straddle vehicle is not limited tomotorcycles but may be another type of vehicle such as a motor tricycle.

What is claimed is:
 1. A straddle vehicle comprising: a prime mover; ahydraulically actuated main clutch disposed in a power transmissionroute between the prime mover and a drive wheel; an oil control valveunit that controls flow of a hydraulic oil supplied to the main clutch;a power unit case that includes a case body and a case cover andaccommodates at least the main clutch in a chamber formed between thecase body and the cover; an oil pan mounted beneath the case body of thepower unit case and retaining an oil; a clutch-dedicated pump that sucksthe oil from the oil pan and that discharges the sucked oil as thehydraulic oil toward the oil control valve unit; a primary filterdisposed in an oil passage between the oil pan and the clutch-dedicatedpump; and a secondary filter disposed in an oil passage between theclutch-dedicated pump and the oil control valve unit, wherein theprimary filter and the secondary filter are mounted on a mountingsurface on a bottom surface of the case body of the power unit case andcovered from below by the oil pan.
 2. The straddle vehicle according toclaim 1, wherein the case body of the power unit case and the oil panare shaped to form together an accommodation chamber in which thesecondary filter is accommodated.
 3. The straddle vehicle according toclaim 1, further comprising: a prime mover-dedicated pump that sucks theoil from the oil pan and discharges the sucked oil toward the primemover to lubricate the prime mover; and another secondary filterdisposed in an oil passage between the prime mover-dedicated pump andthe prime mover, wherein suction inlets of the clutch-dedicated pump andthe prime mover-dedicated pump communicate with the primary filter. 4.The straddle vehicle according to claim 3, wherein the clutch-dedicatedpump and the prime mover-dedicated pump are coaxially connected to eachother.
 5. The straddle vehicle according to claim 1, further comprising:a relief valve disposed between the clutch-dedicated pump and the oilcontrol valve unit; and a bypass passage through which the oildischarged from the relief valve is introduced into an oil passagebetween the primary filter and the clutch-dedicated pump without passingthrough the primary filter.
 6. The straddle vehicle according to claim5, wherein the case body of the power unit case comprises an openingcommunicating with the oil passage between the primary filter and theclutch-dedicated pump, and the case body of the power unit case and theoil pan are shaped to form together a communication chamber as thebypass passage, the communication chamber communicating with the reliefvalve and the opening.
 7. The straddle vehicle according to claim 1,wherein with the oil pan removed, the primary filter and the secondaryfilter are exposed as viewed from below.
 8. A straddle vehiclecomprising: a prime mover; a hydraulically actuated main clutch disposedin a power transmission route between the prime mover and a drive wheel;an oil control valve unit that controls flow of a hydraulic oil suppliedto the main clutch; a power unit case that includes a case body and acover and accommodates at least the main clutch in a chamber formedbetween the case body and the cover; an oil pan mounted beneath the casebody of the power unit case and retaining an oil; a clutch-dedicatedpump that sucks the oil from the oil pan and that discharges the suckedoil as the hydraulic oil toward the oil control valve unit; a primaryfilter disposed in an oil passage between the oil pan and theclutch-dedicated pump; and a secondary filter disposed in an oil passagebetween the clutch-dedicated pump and the oil control valve unit,wherein the primary filter and the secondary filter are mounted on abottom surface of the case body of the power unit case and covered frombelow by the oil pan, the case body of the power unit case and the oilpan are shaped to form together an accommodation chamber in which thesecondary filter is accommodated, the bottom surface of the case body isprovided with a first recessed portion recessed upwardly, a top surfaceof the oil pan is provided with a second recessed portion recesseddownwardly, and the first recessed portion and the second recessedportion form the accommodation chamber.